Lockup clutch released then re-engaged during deceleration control method

Abstract

A method is provided for the control of the state of engagement of a damper clutch arranged in association with a vehicle engine, which has a fuel cut mechanism for suspending a supply of fuel during a decelerated operation, to permit connection between an input member and an output member in a torque converter arranged on an output side of the engine. Upon detection of a decelerated operation of the engine, the damper clutch is controlled to bring the input member and output member into a desired state of engagement. Here, the damper clutch is first released for a predetermined time and is then moved to an engaged side. Next, the damper clutch is feedback-controlled into a desired slip state so that the input member and the output member are allowed to rotate with a desired difference in revolution speed therebetween. A system for practicing the method is also described.

What is claimed is: 
     
       1. A method for controlling an engagement state of a clutch for connecting an input shaft of a fluid coupling and an output shaft of the fluid coupling, the fluid coupling provided between an engine of a vehicle and a transmission, the engine having a fuel cut mechanism for suspending a supply of fuel thereto when an engine load decreases, comprising: (a) detecting said engine load;   (b) releasing said clutch when said engine load decreases;   (c) determining an amount of pressure to be applied to said clutch to move said clutch toward an engaging side and obtain an initial engagement therein;   (d) applying said determined amount to said clutch; and   (e) executing a feedback control of said clutch after obtaining said initial engagement for maintaining a desired rotational speed difference between said input and output shafts of said fluid coupling.   
     
     
       2. The method of claim 1 further comprising: (f) detecting a speed of said vehicle; and wherein said step (c) comprises (c1) determining, from a map, said amount of pressure based on said detected speed and said detected engine load.   
     
     
       3. The method of claim 1 further comprising: (f) detecting a rotational speed of said output shaft; and wherein said step (c) comprises   (c1) determining, from a map, said amount of pressure based on said detected rotational speed and said detected engine load.   
     
     
       4. A method for controlling an engagement state of a clutch for connecting an input shaft of a fluid coupling and an output shaft of the fluid coupling, the fluid coupling provided between an engine and a transmission, the engine having a fuel cut mechanism for suspending a supply of fuel thereto when an engine load decreases, comprising: (a) detecting said engine load;   (b) releasing said clutch when said engine load decreases;   (c) moving said clutch toward an engaging side thereof;   (d) determining a feedback control initiating pressure to be applied to said clutch at an initiation of a feedback control for maintaining a desired rotational speed difference between said input shaft and said output shaft of said fluid coupling based on an operating condition of said vehicle at a time immediately before said engine load decreases;   (e) applying said determined feedback initiating pressure to said clutch after moving said clutch toward said engaging side; and   (f) executing said feedback control after applying said feedback control initiating pressure to said clutch.   
     
     
       5. The method of claim 4, further comprising: (g) detecting a speed of a vehicle; and wherein said step (d) comprises (d1) determining said feedback control initiating pressure based on said detected speed and said detected engine load.   
     
     
       6. The method of claim 4, further comprising: (g) detecting a rotation speed of said output shaft of said fluid coupling; and wherein said step (d) comprises (d1) determining said feedback control initiating pressure based on said detected rotation speed and said detected engine load.   
     
     
       7. A method for controlling an engagement state of a clutch for connecting an input shaft of a fluid coupling and an output shaft of the fluid coupling, the fluid coupling provided between an engine and a transmission, the engine having a fuel cut mechanism for suspending a supply of fuel thereto when an engine load decreases, comprising: (a) detecting said engine load;   (b) releasing said clutch when said engine load decreases;   (c) moving said clutch toward an engaging side thereof;   (d) determining a first feedback control initiating pressure to be applied to said clutch after said engine load decreases to maintain a desired rotational speed difference between said input shaft and said output shaft of said fluid coupling;   (e) applying said determined first feedback initiating pressure to said clutch after moving said clutch toward said engaging side;   (f) executing a first feedback control after applying said determined first feedback initiating pressure to said clutch; and   (g) correcting and storing said first feedback control initiating pressure based on parameters of said first feedback control.   
     
     
       8. The method of claim 7, wherein said step (g) comprises (g1) detecting a first control value obtained upon an elapse of a first predetermined period of time after initiation of said first feedback control;   (g2) detecting a second control value obtained upon an elapse of a second predetermined period of time longer than said first predetermined period of time after initiation of said first feedback control;   (g3) calculating a correction value based on a difference between said first control value and said second control value; and   (g4) correcting and storing said first feedback control initiating pressure to be used as said first feedback control initiating pressure in a subsequent first feedback control based on said calculated correction value.   
     
     
       9. The method of claim 8, wherein said step (g) further comprises (g5) suspending said feedback control when said calculated difference is equal to or greater than a predetermined value.   
     
     
       10. The method of claim 7, further comprising: (h) executing a second feedback control for maintaining a desired rotational speed difference between said input shaft and said output shaft of said fluid coupling before said engine load decreases; and wherein said step (h) comprises   (h1) determining a second feedback control initiating pressure to be applied to said clutch at an initiation of said second feedback control based on said corrected and stored first feedback control initiating pressure.   
     
     
       11. The method of claim 10, wherein said step (h1) comprises (h11) determining said second feedback control initiating pressure such that said second feedback control initiating pressure is less than said first feedback control initiating pressure by a predetermined amount.   
     
     
       12. A method for controlling an engagement state of a clutch for connecting an input shaft of a fluid coupling and an output shaft of the fluid coupling, the fluid coupling provided between an engine and a transmission, the engine having a fuel cut mechanism for suspending a supply of fuel thereto when an engine load decreases, comprising: (a) detecting said engine load;   (b) determining, from a map, a time period for releasing said clutch based on a rotational speed difference between said input shaft and said output shaft of said fluid coupling and said engine load immediately before said engine load decreases;   (c) releasing said clutch for said determined time period;   (d) moving said clutch toward an engaging side thereof; and   (e) executing a feedback control for maintaining a desired rotational speed difference between said input and output shafts of said fluid coupling after moving said clutch toward said engaging side.   
     
     
       13. A clutch engagement state control apparatus, comprising: a fluid coupling having an input shaft connected to an engine and an output shaft connected to a transmission, said engine having a fuel cut mechanism for suspending a supply of fuel thereto when an engine load decreases;   a clutch disposed between said input shaft and said output shaft;   an engine load detector detecting said engine load;   a non-direct connection state routing unit releasing said clutch when said detected engine load decreases;   a determining unit determining an amount of pressure to be applied to said clutch to move said clutch toward an engaging side thereof to obtain an initial engagement;   a pressure feeding unit feeding said determined amount of pressure to said clutch; and   a feedback control unit executing a feedback control after obtaining said initial engagement to maintain a desired rotational speed difference between said input and output shafts of said fluid coupling.   
     
     
       14. A clutch engagement state control apparatus of claim 13, further comprising: a vehicle speed sensor detecting a speed of a vehicle on which said fluid coupling is mounted; and wherein said determining unit comprises   a map for determining said amount of pressure based on said detected speed and said detected engine load.   
     
     
       15. A clutch engagement state control apparatus of claim 13, further comprising: a rotational speed sensor detecting a rotational speed of said output shaft; and wherein   said determining unit comprises   a map for determining said amount of pressure based on   said detected rotational speed and said detected engine load.   
     
     
       16. A clutch engagement state control apparatus, comprising: a fluid coupling having an input shaft connected to an engine and an output shaft connected to a transmission, said engine having a fuel cut mechanism for suspending a supply of fuel thereto when an engine load decreases;   a clutch disposed between said input shaft and said output shaft;   an engine load detector detecting an engine load;   a non-direct connection state routing unit releasing said clutch when said detected engine load decreases;   a first pressure feeding unit moving said clutch toward an engaging side thereof;   a determining unit determining a feedback control initiating pressure to be applied to said clutch to maintain a desired rotational speed difference between said input shaft and said output shaft of said fluid coupling based on an operating condition of said vehicle at a time immediately before said engine load decreases;   a second pressure feeding unit applying said determined feedback initiating pressure to said clutch after moving said clutch toward said engaging side; and   a feedback control unit executing a feedback control after obtaining said initial engagement and after applying said determined feedback control initiating pressure to said clutch.   
     
     
       17. A clutch engagement state control apparatus of claim 16, further comprising: a speed sensor detecting a speed of a vehicle; and wherein said determining unit comprises   an initiating pressure determining unit determining said feedback control initiating pressure based on said detected speed and said detected engine load.   
     
     
       18. A clutch engagement state control apparatus of claim 16, further comprising: a rotation speed sensor detecting a rotation speed of said output shaft of said fluid coupling; and wherein   said determining unit comprises an initiating pressure determining unit determining said feedback control initiating pressure based on said detected rotation speed and said detected engine load.   
     
     
       19. A clutch engagement state control apparatus, comprising: a fluid coupling having an input shaft connected to an engine and an output shaft connected to a transmission, said engine having a fuel cut mechanism for suspending a supply of fuel thereto when an engine load decreases;   a clutch disposed between said input shaft and said output shaft;   an engine load detector detecting an engine load;   a non-direct connection state routing unit releasing said clutch when said detected engine load decreases;   a first pressure feeding unit moving said clutch toward an engaging side thereof;   a determining unit determining a first feedback control initiating pressure to be applied to said clutch after said engine load decreases to maintain a desired rotational speed difference between said input shaft and said output shaft of said fluid coupling;   a second pressure feeding unit applying said determined first feedback initiating pressure to said clutch after moving said clutch toward said engaging side;   a feedback control unit executing a first feedback control after obtaining said initial engagement after applying said determined first feedback control initiating pressure to said clutch; and   a correcting and storing unit correcting and storing said first feedback control initiating pressure based on parameters of said first feedback control.   
     
     
       20. A clutch engagement state control apparatus of claim 19, wherein said correcting and storing unit comprises   a first control value detecting unit detecting a first control value obtained upon an elapse of a first predetermined period of time after initiation of said first feedback control;   a second control value detecting unit detecting a second control value obtained upon an elapse of a second predetermined period after initiation of said first feedback control, said second predetermined period of time being longer than said first predetermined period of time;   a calculating unit calculating a correction value based on a difference between said first control value and said second control value; and   a learning unit correcting and storing said first feedback control initiating pressure to be used as said first feedback control initiating pressure in a subsequent first feedback control based on said calculated correction value.   
     
     
       21. A clutch engagement state control apparatus of claim 20, wherein said correcting and storing unit further comprises   a suspending unit suspending said first feedback control when said calculated difference is equal to or greater than a predetermined value.   
     
     
       22. A clutch engagement state control apparatus of claim 19, further comprising: a control unit executing a second feedback control for maintaining a desired rotational speed difference between said input shaft and said output shaft of said fluid coupling before said engine load decreases; and wherein   said control unit comprises   an initiating pressure determining unit determining a second feedback control initiating pressure to be applied to said clutch at an initiation of said second feedback control based on said corrected and stored first feedback control initiating pressure.   
     
     
       23. A clutch engagement state control apparatus of claim 22, wherein said initiating pressure determining unit determines said second feedback control initiating pressure such that said second feedback control initiating pressure is less than said first feedback control initiating pressure by a predetermined amount.   
     
     
       24. A clutch engagement state control apparatus, comprising: a fluid coupling having an input shaft connected to an engine and an output shaft connected to a transmission, said engine having a fuel cut mechanism for suspending a supply of fuel thereto when as engine load decreases;   a clutch disposed between said input shaft and said output shaft;   an engine load detector detecting an engine load;   a speed difference detection unit detecting a rotation speed difference between said input shaft and said output shaft of said fluid coupling;   a determining unit determining, from a map, a time period for releasing said clutch based on said detected rotational speed difference and said detected engine load obtained immediately before said engine load decreases;   a non-direct connection state routing unit releasing said clutch for said determined time period;   a pressure feeding unit moving said clutch toward an engaging side thereof after said determined time period; and   feedback control unit executing a feedback control for maintaining a desired rotational speed difference between said input shaft and said output shaft of said fluid coupling after moving said clutch toward said engaging side.